This invention relates in general to a lubricant used during the manufacture of intravenous (IV) catheters. In addition, this invention relates to a lubricant solution that facilitates application of the lubricant to a surface and that uses water as the carrier or solvent.
IV catheters are designed to infuse normal intravenous solutions, including antibiotics and other drugs, into a patient. These catheters are also used to withdraw blood from the patient for normal blood-gas analysis as well as other blood work.
The typical catheter is hollow and is extruded out of suitable plastic material such as Teflon, polyvinyl chloride, polyethylene, polyurethane or polyether urethane. In order to insert a catheter into a patient, an introducer needle is used. The needle is typically formed from stainless steel and is hollow. Its distal tip is ground to a sharp tip for easy insertion into the patient. The catheter is initially located coaxially around the introducer needle in an "over the needle" arrangement. The internal diameter of the catheter tip is slightly less than the outer diameter of the needle so that the catheter tip has an interference fit on the needle. The interference fit is necessary so that when the catheter and introducer needle assembly is taken out of the package, the catheter remains snugly on the needle and does not easily slip off. This interference fit also facilitates insertion of the catheter and introducer needle assembly into the patient's vein because it minimizes the chance that the catheter tip will fold over or peel back on the needle tip.
Placement of the catheter and introducer needle assembly into the patient causes sharp pain to the patient. In order to facilitate insertion of the assembly into the vein and to minimize patient discomfort, the shape of the catheter tip is formed so as to produce minimal trauma to the patient during insertion of the catheter into the patient and while the catheter is in place in the patient. Such a preferred tip shape that provides these characteristics has a tapered outer wall and an angled tip and disclosed in U.S. Pat. No. 4,588,398. A process for making that catheter tip, known as the tipping process, is disclosed in U.S. Pat. No. 4,661,300. In this tipping process, the catheter blank is placed on a mandrel. A die having an interior molding surface, which is tapered according to the tip desired on the catheter, is aligned axially with the mandrel. The tip of the catheter blank is heated, typically using RF energy, so that it is flowable. The mandrel and die are brought together so the distal edge of the mandrel engages the tapered portion of the die. This action cleanly forms a smooth and uniform tapered tip for the catheter.
After the catheter is tipped, it must be free of defects such as incomplete formation, substantial flash or jagged edges. The tip must also look smooth and be free of roll-overs. In addition, the length of the catheter must remain within a desired specification after the tipping process. Visual or microscopic examination may be used to determine if there are any tip defects and if the length of the catheter is within specifications. Typically a lubricant is used to allow the tipped catheter to be easily removed from the mandrel and die. If a lubricant is not used, the tipped catheter could stick to the mandrel or die resulting in a deformed catheter when it is removed from the mandrel or die.
Standard tipping lubricants include polydimethyl siloxanes such as Dow Corning DC 360 or curable silicones such as Dow Corning 44159 MDX which are amine terminated and moisture curable. Non-curable amine terminated polydimethyl siloxanes have also been used for this purpose. Such lubricants are described in, for example, U.S. Pat. Nos. 3,574,673; 4,664,657; 4,904,433; and 5,185,006.
An additional mechanism that is used to facilitate insertion of the catheter and introducer needle assembly into the patient is lubrication. Typically the catheter will be lubricated to minimize drag between the catheter and the patient's skin. In addition, lubricant can be applied to the needle to minimize adhesion between the catheter and the needle to facilitate removal of the needle from the catheter. Such catheter and needle lubricants include the same type of lubricants that have heretofore been used during the tipping process.
The amount of lubricant needed to provide lubricity to the catheter, between the catheter and the needle and between the catheter blank and the mandrel and die during the tipping process is very small. Thus in order to control the application of the lubricant, the surface to be lubricated is coated with a lubricant solution that contains the lubricant and a carrier or solvent. Use of a lubricant solution also facilitates application of the lubricant to the inside surface as well as outside surface of the catheter. After the lubricant solution is applied to the surface, the carrier or solvent evaporates leaving the lubricant behind on the surface of the catheter. The silicone oils used as typical lubricants are hydrophobic. Therefore, these compounds must be dissolved in organic solvents in order to prepare a lubricant solution which can be applied to the surface to be lubricated before the tipping process can begin. The primary solvent that has been used heretofore is freon because it is nonflammable and evaporates quickly. Unfortunately, because of recent concerns that chlorofluorocarbons (CFC) react with and destroy the earth's protective ozone layer, the production and use of CFC will cease in the near future. Thus other solvents must be used. Other organic solvents, such as alcohols and hydrocarbons, are highly flammable. Thus, it is too dangerous to use large amounts of these solvents in the tipping process.